AUSTIN AND HOUSTON - A partnership composed of Clarion Partners LLC and Private Mini Storage, has sold for $257.9 million a 30-property, 2.4 million-sf portfolio of self-storage facilities.

The buyer was CubeSmart, a REIT that is the nation’s fourth-largest owner-operator of self-storage facilities. All but one of the properties are in metro Houston and Austin — the other one is in metro Charlotte, N.C.

The acquisition, according to Clarion, gives the purchaser “an excellent opportunity to acquire a geographic concentration and critical operating mass” in both Houston and Austin.

The current overall occupancy rate is 88 percent.

Clarion and Private Mini had been partners in the ownership of the portfolio since 2005. As of the end of 2012, CubeSmart owned 381 self-storage facilities in 22 states and the District of Columbia totaling about 25.5 million rentable sf.